Do not verify on state import for relay chain verifier (paritytech#2140)

* Skip verification on state import

* Actually use existing variables

* Merge checks

client/consensus/relay-chain/src/import_queue.rs

@@ -58,6 +58,14 @@ where
 		&mut self,
 		mut block_params: BlockImportParams<Block, ()>,
 	) -> Result<(BlockImportParams<Block, ()>, Option<Vec<(CacheKeyId, Vec<u8>)>>), String> {
+		// Skip checks that include execution, if being told so, or when importing only state.
+		//
+		// This is done for example when gap syncing and it is expected that the block after the gap
+		// was checked/chosen properly, e.g. by warp syncing to this block using a finality proof.
+		if block_params.state_action.skip_execution_checks() || block_params.with_state() {
+			return Ok((block_params, Default::default()))
+		}
+
 		if let Some(inner_body) = block_params.body.take() {
 			let inherent_data_providers = self
 				.create_inherent_data_providers